(1) Field of the Invention:
This invention relates to blow molding devices in which thermoplastic materials such as resins are shaped into various hollow articles.
(2) Description of the Prior Arts:
Typical patents illustrating the prior art comprise U.S. Pat. Nos. 3,325,860; 3,640,672; 3,806,587; 3,899,279; 3,910,746 and 3,969,060. Each of these several prior art patents discloses a blow molding device and each is directed to some specific improvement.
In U.S. Pat. No. 3,325,860 the improvement related to providing the mold sections with suction nozzles for applying suction to the outside of the upper end of the parison within the mold.
In U.S. Pat. No. 3,640,672 the improvement provides the formation of the blow pin with openings arranged so that air blown through one of the openings blows the container body and the air directed through the other opening blows the handle of the particular article disclosed in the patent.
In U.S. Pat. No. 3,806,587 a principal point of novelty relates to the arrangement of the apparatus for stretching a pinched portion of the parison while the latter is in a closed mold prior to or during the inflation of the pinched parison portion which has been chilled to partially reduce the temperature thereof.
In U.S. Pat. No. 3,899,279 the novelty comprises the formation of a blow mold with neck forming jaws with spaced apart choke rings which restrict the movement of the thermoplastic material from the neck area of the container during the formation of the same.
U.S. Pat. No. 3,910,746; a blow molding apparatus is disclosed which includes an improved cooling system to rapidly reduce the temperature of the thermoplastic material by introducing a coolant directly into the blown article.
In U.S. Pat. No. 3,969,060 blow molding apparatus is disclosed in which the parison of thermoplastic material is preheated and then gripped so as to reduce the cross section of the gripped portion which results in the deformation of the gripped portion to provide a desired profile formation.
None of the prior art of the aforesaid patents disclose blow molding devices wherein blow molds and more particularly the neck ring or shear insert thereof is provided with notches in the engaging portions thereof which define the pinch-off of the thermoplastic material on the so called pinch-off line of the article being formed so that additional quantities of the thermoplastic material are present in indicated critical areas which can then be smoothed by the withdrawing blow pin and mandrel to form a smooth inner annular surface completely eliminating the pinch off groove heretofore formed on the inner surface of a hollow article formed in accordance with the prior art techniques.